The invention is in the technical field of bubbling fluidized bed combustion and relates to the use of ilmenite particles with an average particle size <dp> between 0.1 mm and 1.8 mm as bed material for a bubbling fluidized bed (BFB) boiler with an excess air ratio () below 1.3 and to a method for operating a bubbling fluidized bed (BFB) boiler, comprising carrying out the combustion process with a bubbling fluidized bed comprising ilmenite particles as defined in any one of claims 1 and 4-5; and setting the excess air ratio () to a value below 1.3.

The invention is in the technical field of bubbling fluidized bed combustion and relates to the use of ilmenite particles with an average particle size <dp> between 0.1 mm and 1.8 mm as bed material for a bubbling fluidized bed (BFB) boiler with an excess air ratio () below 1.3 and to a method for operating a bubbling fluidized bed (BFB) boiler, comprising carrying out the combustion process with a bubbling fluidized bed comprising ilmenite particles as defined in any one of claims 1 and 4-5; and setting the excess air ratio () to a value below 1.3.

A continuous char separation reactor (800) comprising a container (301) configured to contain a bed of char and bed solids and a settling zone (122) disposed within a first region of the container and configured to receive an input flow (180) comprising the char and bed solids. The settling zone (122) comprises a settling means (334) configured to segregate the received char and bed solids into a char fraction (001) having a ratio of char to bed solids that is at least 5 larger than that of the input flow (180) and a depleted portion (002) of the bed solids having a lower ratio of char to bed solids than that of the input flow.